CN106576327B - Method for dynamically reducing fronthaul load between base station and plurality of remote radio units - Google Patents

Method for dynamically reducing fronthaul load between base station and plurality of remote radio units Download PDF

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CN106576327B
CN106576327B CN201480081089.7A CN201480081089A CN106576327B CN 106576327 B CN106576327 B CN 106576327B CN 201480081089 A CN201480081089 A CN 201480081089A CN 106576327 B CN106576327 B CN 106576327B
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allocated
data
radio resources
remote unit
unit
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CN106576327A (en
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M·博尔迪
P·吉阿诺拉
B·麦利斯
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Telecom Italia SpA
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Telecom Italia SpA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/29—Control channels or signalling for resource management between an access point and the access point controlling device
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/52—Allocation or scheduling criteria for wireless resources based on load
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/085—Access point devices with remote components

Abstract

It is proposed to arrange a User Equipment (UE) in a mobile communication network (100)i) And at least one Base Station (BS)* INFOi,n,S* CTRLn) The at least one Base Station (BS) comprising a Central Unit (CU) and at least one Remote Unit (RU) associated therewithj) Wherein said data (S)* INFOi,n,S* CTRLn) Comprising from a Central Unit (CU) to said at least one Remote Unit (RU)j) Or from said at least one Remote Unit (RU)j) Information data (S) to a Central Unit (CU)* INFOi,n) And control data (S)* CTRLn). The method comprises the following steps: for data to/from said at least one Remote Unit (RU)j) Is said data (S)* INFOi,n,S* CTRLn) Allocating (115) radio resources, the radio resources (P) to be allocatedPRBp) Grouping (120) into allocated radio resource groups (AG)g,n) Each allocated radio resource group (AG)g,n) Including for communication to/from respective Remote Units (RUs)j) Data (S) of* INFOi,n,S* CTRLn) Allocated at least one radio resource (P)PRBp) Will associate data (A)SSD) Comprising (120) at each allocated radio resource group (AG)g,n) The associated data (A)SSD) Indicating the allocated radio resource group (AG)g,n) Of said at least one allocated radio resource (P)PRBp) And corresponding Remote Unit (RU)j) Will assign data (A)LLD) Comprising (120) at each allocated radio resource group (AG)g,n) In (b), the allocation data (A)LLD) Indicating the at least one allocated radio resource (P)PRBp) In which at least information data (S) has been aligned* INFOi,n) Allocated radio resources (P)PRBp) And a set of radio resources (AG) to be allocatedg,n) In the frequency domain at a Central Unit (CU) and at the at least one Remote Unit (RU)j) And (4) are transmitted.

Description

Method for dynamically reducing fronthaul load between base station and plurality of remote radio units
Technical Field
The present invention relates generally to mobile communication networks-hereinafter referred to as mobile networks. More particularly, the invention relates to mobile networks based on a "centralized radio access network" (CRAN) architecture.
The work leading to the present invention has received funding from the European Union seventh framework project FP7/2007 and 2013 under the grant agreement n.317941, project iJOIN.
Background
A CRAN typically comprises one or more central units, each connected to a plurality of remote units (preferably by means of respective optical fibre links).
According to the conventional CRAN architecture, in the downlink, a central unit receives data to be transmitted to user equipments of the mobile network and provides a digital baseband signal. The digital baseband signal is then converted from electrical to optical and transmitted to the remote unit over the fiber optic link. Each remote unit receives an optical baseband signal which is then converted from optical to electrical, filtered, converted from digital to analog, up-converted (up-converted) from baseband to radio frequency, and amplified before being radiated by the antenna to the user equipment.
In OFDMA ("orthogonal frequency division multiple access") based radio access technologies such as WiMAX ("worldwide interoperability for microwave access") and LTE ("long term evolution")/LTE-a ("LTE-advanced"), the digital baseband signal is a composite digital baseband signal, i.e. it consists of signals for different user equipments (or user signals) superimposed in the time domain.
Each conventional CRAN (based on optical fiber links) thus provides for the transmission of one (optical) composite baseband signal per (transmission) antenna per remote unit (over an optical fiber link) when downlink is considered, or for each (reception) antenna per remote unit (over an optical fiber link) when uplink is considered, where such transmission occurs in the time domain (e.g. according to the "open base station architecture alliance" (OBSAI) or "common public radio interface" (CPRI) standards). As a result thereof, the transmission capacity available over the fiber optic link can quickly become a bottleneck as the number of remote units connected to a given central unit increases. In addition, the transmission capacity available on the fiber link may also be saturated by a relatively low number of signals, especially when considering new radio access technology applications-and further increasing data rates are expected with upcoming technologies such as "multiple input multiple output" (MIMO) and carrier aggregation technologies.
Some prior art solutions have addressed such problems.
Signal processing algorithms have been proposed that operate separately on each user signal (such as "adaptive beamforming" and "network coordination" algorithms).
WO2006/102919, "a radio Access Method, related base station, mobile radio-network and computer program product using an association scheme for antenna' sectors" discloses a system comprising a radio base station for a mobile network and a set of remote units connected to the radio base station, preferably via a "radio over fiber" (ROF) arrangement. Each remote unit provides radio coverage via a set of communication channels and is equipped with a corresponding set of antenna elements. The communication channels are distributed over the antenna elements according to a dynamically variable allocation scheme.
WO2010/075864, "a Method for distributed Mobile Communications, correcting system and computer program product" discloses a Method of arranging the exchange of signals between a user terminal and at least one base station in a cellular communication system. The base station includes a central unit and a plurality of remote units. The signals are exchanged between the central unit and the remote unit as aggregated signals of a plurality of user devices. The signals are processed at the remote unit as distinct signals each associated with a respective one of the plurality of user devices. In particular, WO2010/075864 shows a method of reducing data on fibre radio links (commonly referred to as "fronthaul" (fronthaul) links) based on frequency domain transmission, in order to distinguish these links from "backhaul" links that instead connect the central unit to the mobile transport network. This is achieved by arranging the IFFT/FFT modules in the remote unit and transmitting the signals in the frequency domain.
Disclosure of Invention
The applicant has found that the above cited solutions are not entirely satisfactory for modern technical requirements.
In particular, the applicant has found that the traditional CRAN architecture, in which signal processing operations are delegated to a central unit, is affected by flexibility problems, since any algorithm change may involve software and/or hardware modifications in the central unit, and by scalability problems, since it involves a limitation of the maximum number of remote units that can be connected to a given central unit.
These problems are exacerbated in the CRAN architecture which relies on signal processing algorithms that operate separately on each user signal, such as "adaptive beamforming" and "network coordination" algorithms, as the application of such algorithms requires signal processing operations to be performed on the central unit side (where the user signals are still separately available), thus further burdening the central unit. The applicant has therefore appreciated that in order to effectively apply such an algorithm, the data rate of the signals transmitted over the optical fibre link should be reduced.
The applicant has found that although the frequency domain transmission methods disclosed in WO2006/102919 and WO2010/075864 allow the data rate to be relatively reduced relative to conventional time domain based methods, the data rate of the signals transmitted over the optical fibre link should be further reduced in order to meet the increasing modern demands of the maximum number of remote units that can be connected to a given central unit.
In view of the above, the applicant has devised a solution aimed at overcoming these and other drawbacks. Specifically, the applicant has devised systems and methods for dynamically reducing the fronthaul load (load), including information and control data, by transmitting in the frequency domain only radio resources that have been allocated at least for information data.
One or more aspects of the solution according to an embodiment of the invention are set out in the independent claims, wherein advantageous features of the solution are set out in the dependent claims (the wording of which is included herein verbatim by reference).
More particularly, the solution according to an embodiment of the invention relates to a method of arranging transmission of data between a user equipment and at least one base station in a mobile communication network, said at least one base station comprising a central unit and at least one remote unit associated therewith. The data comprises information data and control data from the central unit to the at least one remote unit or from the at least one remote unit to the central unit. The method comprises the following steps:
allocating radio resources for said data to/from said at least one remote unit,
grouping the allocated radio resources into allocated sets of radio resources, each allocated set of radio resources comprising at least one radio resource allocated for data to/from a respective remote unit,
including association data in each allocated set of radio resources, the association data indicating an association of the at least one allocated radio resource of that allocated set of radio resources with a respective remote unit,
including allocation data in each allocated set of radio resources, the allocation data indicating allocated radio resources among the at least one allocated radio resource that have been allocated at least for information data, an
Transmitting the allocated set of radio resources in the frequency domain between the central unit and the at least one remote unit.
According to an embodiment of the invention, said transmitting said allocated set of radio resources in the frequency domain between the central unit and said at least one remote unit comprises: for each allocated set of radio resources, only allocated radio resources that have been allocated at least for information data among the at least one allocated radio resources of the allocated set of radio resources are transmitted.
According to an embodiment of the invention, the association data comprise a maximum number of bits (bit) depending on the remote units that can be associated with the central unit, each bit being associated with a respective remote unit and being set to a first logical value if the allocated radio resources of the set of allocated radio resources considered are associated with this remote unit and to a second logical value otherwise.
According to an embodiment of the invention, the allocation data comprises a number of bits depending on a maximum number of radio resources available for allocation, each bit being associated with a respective radio resource and being set to a first logical value if said respective radio resource has been allocated at least for the information data and to a second logical value otherwise.
According to an embodiment of the invention, the allocation data further comprises at least one further bit associated with each radio resource, the at least one further bit providing an indication of a modulation scheme used for modulation of data on the allocated radio resource.
According to an embodiment of the invention, said transmitting said allocated set of radio resources in the frequency domain between the central unit and said at least one remote unit comprises transmitting each set of radio resources in turn.
According to an embodiment of the invention, said transmitting said allocated set of radio resources in the frequency domain between the central unit and said at least one remote unit comprises transmitting association and allocation data for each set of radio resources before allocated radio resources of that set of radio resources.
According to an embodiment of the invention, the data is "orthogonal frequency division multiplexing" data.
According to an embodiment of the invention, said grouping and said including are performed on the side of the central unit when the set of radio resources is transmitted from the central unit to the at least one remote unit, and on the side of the at least one remote unit when the set of radio resources is transmitted from the at least one remote unit to the central unit.
Another aspect of the solution according to embodiments of the invention relates to a system for exchanging data with a user equipment in a mobile communication network. The system comprises a central unit adapted to be associated with at least one remote unit and the data comprises information data and control data from the central unit to the at least one remote unit. The central unit is configured to:
allocating radio resources to the data destined for the at least one remote unit,
grouping the allocated radio resources into allocated sets of radio resources, each allocated set of radio resources comprising at least one radio resource allocated for data destined for a respective remote unit,
including association data in each allocated set of radio resources, the association data indicating an association of the at least one allocated radio resource of that allocated set of radio resources with a respective remote unit,
including allocation data in each allocated set of radio resources, the allocation data indicating allocated radio resources among the at least one allocated radio resource that have been allocated at least for information data, an
Transmitting the allocated set of radio resources in the frequency domain between the central unit and the at least one remote unit.
According to an embodiment of the invention, the system further comprises said at least one remote unit.
According to an embodiment of the invention, the at least one remote unit is connected to the central unit by means of a fiber optic link.
According to an embodiment of the invention, the at least one remote unit is connected to the central unit by means of a wireless communication link.
A further aspect of the solution according to an embodiment of the invention relates to a computer program product for performing the above method when the computer program product is run on a computer.
Drawings
These and other features and advantages of the present invention will become apparent from the following description of some exemplary and non-limiting embodiments thereof. For better intelligibility thereof, the following description should be read with reference to the accompanying drawings, in which:
FIGS. 1A-1B schematically illustrate a mobile communications network and portions thereof, respectively, according to embodiments of the present invention, and
fig. 2 is a schematic representation of an exemplary allocated set of radio resources according to an embodiment of the present invention.
Detailed Description
Referring to the drawings, fig. 1A-1B schematically illustrate a mobile communication network (hereinafter, mobile network) 100 and portions thereof, respectively, according to an embodiment of the present invention.
Mobile network 100 allows data to be transmitted at user equipment UEi(I ═ 1,2, …, I) (such as user equipment UE)1-UE5(I-5)) and one or more base stations, such as base station BS.
The mobile network 100 conforms to, for example, 3GPP LTE/LTE-advanced or WiMAX standards. The principles of the present invention are however generally applicable to any mobile network based on OFDM ("orthogonal frequency division multiplexing") technology and are particularly advantageous when applied to mobile networks further based on MIMO ("multiple input multiple output") technology.
According to the OFDM technique, data to be transmitted (including both information data and control data) is divided into data sequences that are modulated by separate and mutually orthogonal subcarriers and multiplexed into a data stream comprising OFDM symbols or a stream of OFDM symbols for transmission. According to the MIMO technique, a plurality of OFDM symbol streams are transmitted/received via a plurality of transmission/reception antennas, which improves communication performance without additional bandwidth or increased transmission power.
As is known, OFDM technology is based on radio resource allocation in the time/frequency domain. Considering, for example, the 3GPP LTE/LTE-advanced standard, the radio resources are distributed in the time domain every "transmission time interval" (TTI), each lasting 1ms (subframe) and comprising two 0.5ms time slots, while in the frequency domain the whole bandwidth is divided into a plurality of 180-kHz subchannels (each corresponding to 12 adjacent and equal to each other)Ground-spaced subcarriers). A radio resource comprising a plurality of OFDM symbols (e.g., seven) spanning one slot in the time domain and twelve adjacent subcarriers in the frequency domain is called a "physical resource block" (PRB) and corresponds to a resource that can be allocated to an ith user equipment UEiWith minimum radio resources for transmission.
According to a preferred, but not limiting, illustrative embodiment, the mobile network 100 is based on a "centralized radio access network" (CRAN) architecture/system, wherein each base station BS (or at least one of the base stations of the mobile network 100) comprises a central unit (such as a central unit CU) and one or more remote units RU associated therewith (e.g. coupled or connected thereto)jJ-1, 2, …, J, where J-3 in the example in question. As shown, the central unit CU is preferably connected to the remote units RU on one sidej(e.g. by means of (ring) optical fibre links FL(also referred to as fronthaul link)) and on the other side to the core network CN (e.g., by means of a suitable wired or wireless link, also referred to as backhaul link). Each remote unit RUjComprising a number K of transmission/reception antennas Aj,k(K-1, …, K, where K-2 in the example in question) for transmitting data from the central unit CU to a plurality of user equipments UEi(and thus to multiple remote units RU)j) And for data from a plurality of user equipments, UEsi(and thus from multiple remote units RU)j) To the central unit CU (hereinafter such bidirectional data transmission, i.e. downlink and uplink transmission, also referred to for brevity as to/from a plurality of user equipments UEiData transmission of (c).
In the following, for the purpose of discussing the actual scenario, we will exemplarily refer to the CRAN architecture, where the baseband functionality is distributed between the central unit CU and the remote units RUjIn the meantime. Such a CRAN architecture, which is thoroughly discussed in WO2010/075864, is now well known in the art, and therefore only relevant aspects thereof that are strictly necessary for understanding the present invention will be introduced and described hereinafter (with some other aspects being intentionally omitted for the sake of brevity).
Furthermore, in the following description, reference will be made only exemplarily to downlink transmission, it being understood that the present invention is equally applicable to uplink transmission as well.
As shown in fig. 1B, the central unit CU comprises a control module 105 implementing higher layer protocols, such as the "radio resource control" (RRC), "radio link control" (RLC) and "medium access control" (MAC) layers, for receiving a plurality of user equipments UEiFor example via a conventional S1 interface and for providing the inclusion information DSINFOAnd control DSCTRL,1(such as pilot and synchronization) of corresponding "transport blocks" of channels or data streams to a plurality of user equipments, UEsi。
The central unit CU further comprises a processing module 110, the processing module 110 being adapted to receive the information data stream DSINFOAnd for each ith user equipment UEiProviding a number NSN (e.g., N in the multi-antenna scenario considered herein)SNot less than 1) stream of information symbols SINFOi,n(in the same user equipment UE as the ithiAssociated NSEach nth information symbol stream of the plurality of information symbol streams comprises a plurality of information symbols sINFOi,n) And for receiving a control data stream DSCTRLAnd providing NSA corresponding control symbol stream SCTRLn(in N)SEach nth control symbol stream of the plurality of control symbol streams includes a plurality of control symbols sCTRLn)。
To achieve this, the processing module 110 is preferably configured to process the information data stream DSINFOPerforming coding processes (e.g. including the well-known "cyclic redundancy code" insertion, segmentation, channel coding, rate matching-i.e. puncturing/repetition-operations), error correction processes (e.g. by means of "hybrid automatic repeat request" (H-ARQ) operations that manage retransmissions at the physical level by means of, for example, "Chase combining" or "incremental redundancy" techniques) and interleaving, modulation and MIMO processing (e.g. based on "spatial multiplexing" or on "space-time/frequency coding"), and controlling the data stream DSCTRLPerforms code interleaving, modulation and MIMO processing (in effect, on the control data stream DS)CTRLH-ARQ operations are not typically requiredAs the latter are typically transmitted by means of robust channel coding schemes).
The central unit CU further comprises a modulation/mapping module 115, the modulation/mapping module 115 being configured to receive the information SINFOi,nAnd control SCTRLnA stream of symbols and modulating information sINFOi,nAnd control sCTRLnSymbol, thereby obtaining corresponding information s* INFOi,nAnd control s* CTRLnOFDM symbol (and corresponding information S)* INFOi,nAnd control S* CTRLnA stream of OFDM symbols). The modulation is preferably done according to a suitable radio resource allocation scheduling function (e.g. residing at the MAC layer) -as conceptually illustrated in the figure by the arrow connection denoted by the word "RRA schedule" from the control module 105 to the modulation/mapping module 115.
Although not shown, the information S* INFOi,nAnd control S* CTRLnThe OFDM symbol stream is then subjected to electrical to optical conversion and passed through an optical fiber (fronthaul) link FLIs transmitted to remote unit RUiFor example by means of a standard transport format defined by an international alliance such as CPRI ("common public radio interface") or OBSAI ("open base station architecture alliance").
As can be seen in the figure, the modulation/mapping module 115 is further configured to receive the information DSINFOAnd control DSCTRLData flows and mapping them to N under control of a radio resource allocation scheduling functionSIndividual time-frequency radio resource grid (grid) TFGnIn (1). Every nth time-frequency radio resource grid TFGnContains the complete set of available PRBs and identifies among them the UE for all I user equipmentsiOf the nth information OFDM symbol stream S* INFOi,nAnd for the nth control OFDM symbol stream S* CTRLnThe allocated PRBs. Although not shown, the mathematical relationship, formula or dynamic lookup table defining said mapping is preferably provided by the central unit CU to the remote units RU in the form of control information (e.g. refreshed at a refresh rate corresponding to a transmission frame or to a scheduling period)j(e.g., for demapping operations).
Every nth time-frequency radio resource grid TFGnConceptually, a matrix with a number R of rows equal to the number of radio resources (i.e., OFDM subcarriers in the example at issue) used for transmission and a number C of columns equal to the number of OFDM symbols in one frame period.
According to the invention, the central unit CU comprises a TFG for appropriately formatting the n-th time-frequency grid, as discussed belownOf the actual PRB contained in the block 120.
Preliminarily, as should be appreciated, the term "module," particularly in relation to the formatting module 120, is intended herein to contemplate either a hardware or software implementation thereof. In the case of a software implementation, the operational steps may be implemented by suitable code means included in a computer program and executed when the program is run on a computer.
The formatting module 120 is configured to group allocated PRBs to be in the frequency domain over the fiber link FLNumber of transmissions G allocated PRB group AGg,n-AGg,nTFG with nth time-frequency grid among PRB groups representing G allocationsnAn associated g-th allocated PRB group. As will be understood shortly, the allocated PRB group AGg,nIs dependent on the number G of user equipments UEiAssociated actual data payload, e.g. n-th time-frequency grid TFGnAnd may be according to the nth time-frequency grid under consideration TFGnAnd (4) changing. Thus, each g-th allocated PRB group AGg,nIncluding RU for communication to/from respective remote unitsjAt least one PRB of the data allocation.
Furthermore, the formatting module 120 is configured to associate association data and allocation data to each g-th allocated PRB group AGg,n. Broadly speaking, the association data and allocation data are intended to allow a time-frequency radio resource grid TFGnAs better discussed below. Thus, as a result of the association, each g-th allocated PRB group AGg,nCorresponding association data and assignment data are also included.
As should be readily appreciated, the formatting is at the allocated PRB group AGg,nIs transmitted from the central unit CU to the remote units RUjIs executed (from a logical point of view) on the central unit CU side, but on the allocated PRB group AGg,nSlave remote unit RUjRemote unit RU when transmitting to central unit CUjSide execution.
Referring jointly to fig. 2, a generalized nth time-frequency grid TFG is schematically illustratednG-3 exemplary allocated PRB group AGg,n(Again, for one central unit CU and three remote units RU shown in FIGS. 1A-1B1-RU3Scenario) of each g-th allocated PRB group AGg,nThe method comprises the following steps:
-allocated PRB pairs PPRBp(P ═ 1,2, … P, where P depends on the channel bandwidth) -it is allocated to the respective user equipment UEi(and thus to the respective remote units RUi) E.g. n time-frequency grid TFGnAs indicated in (a). By way of example only, an allocated PRB pair P of P6 is considered hereinPRBp. As can be seen from the example in the figure, the first allocated PRB group AGg,n(i.e., allocated PRB group AG)1,n) Includes an allocated PRB pair PPRB3、PPRB5、PPRB6Second allocated PRB group AGg,n(i.e., allocated PRB group AG)2,n) Includes an allocated PRB pair PPRB1、PPRB2And a third allocated PRB group AGg,n(i.e., allocated PRB group AG)3,n) Includes an allocated PRB pair PPRB1、PPRB2、PPRB3、PPRB4、PPRB5。
-associated data ASSD, the associated data ASSD indicates the allocated PRB group AGg,nAllocated PRBs (i.e. allocated PRB pair P in the considered example)PRBp) And corresponding remote unit RUi(and thus with corresponding user equipment, UE)i) The association of (a). According to the illustrated embodiment, the association data ASSD is in the form of a bitmap, the number of bits of which depends on the distance that can be associated with the central unit CUProgram unit RUjThe maximum number of (c). Preferably, each jth bit is associated with a corresponding jth remote unit RUjAssociated and if the g-th allocated PRB group AG under considerationg,nAllocated PRB pair PPRBpWith the jth remote unit RUjAssociated, each jth bit is set to a first logical value (e.g., a high or "1" logical value) and otherwise to a second logical value (e.g., a low or "0" logical value). Thus, three remote units RU under considerationjIn the example of (2), the first allocated PRB group AG1,nAssociated data A ofSSD includes a bitmap "100", which bitmap "100" identifies, for example, a remote unit RU1Second allocation of PRB group AG2,nAssociated data A ofSSD includes a bitmap "010" identifying, for example, a remote unit RU2And a third allocated PRB group AG3,nAssociated data A ofSSD includes a bitmap "001", which bitmap "001" identifies, for example, a remote unit RU3. Thus, in the example considered, only the allocated PRB pair PPRB3、PPRB5、PPRB6Is transmitted to remote unit RU1Allocated PRB pairs P onlyPRB1、PPRB2Is transmitted to remote unit RU2And only allocated PRB pairs PPRB1、PPRB2、PPRB3、PPRB4、PPRB5Is transmitted to remote unit RU3。
-allocation data ALLD, the distribution data ALLD indicates the allocated PRB group AG under considerationg,nOf allocated PRB pairs that have been allocated at least for information data (i.e. allocated PRB pair P in the example consideredPRBp). According to an embodiment of the present invention, as shown in the figure, data A is allocatedLLD is in the form of a bitmap, the number of bits of which depends on the maximum number of allocated PRB pairs available for transmission in a given subframe. Each bit may correspond to a corresponding allocated PRB pair PPRBpAssociated and if the corresponding PRB pair PPRBpThe PRB pairs P that have been allocated at least to information data (i.e., to both control data and information data, or to information data only, hereinafter referred to as information)PRBp) Allocation, then each bit is set to a high (or low) logic value, otherwise to a low (or high) logic value (hereinafter referred to as controlling allocated PRB pair P)PRBpI.e. allocated PRB pairs P carrying only control data, such as pilot and synchronization dataPRBp). According to a different embodiment of the invention, not shown, data A is distributedLLD further comprises a PRB pair P with each allocationPRBpAssociated at least one further bit providing an indication of a modulation scheme (e.g., QPSK, 16-QAM, 64-QAM) used to modulate the data on the radio resource. According to such an embodiment, data A is allocatedLLD may be in the form of a bitmap, the number of bit pairs of which depends on (e.g., is equal to) the available allocated PRB pairs PPRBpWherein each bit pair is associated with a respective allocated PRB pair PPRBpAnd (4) associating. By way of example only, a bit pair of "00" may indicate a PRB pair P that controls allocationPRBpBit pair "01" may indicate the PRB pair P of the information allocationPRBpAnd QPSK modulation scheme, a bit pair "10" may indicate a PRB pair P for information allocationPRBpAnd 16-QAM modulation scheme, and bit pair "11" may indicate PRB pair P of information allocationPRBpAnd a 64-QAM modulation scheme.
After the formatting, the resulting allocated PRB group AGg,nThen via electrical to optical conversion (not shown) and through (fronthaul) fiber optic link FLIs transmitted to remote unit RUi。
As should be readily understood, in the exemplary scenario considered, in which the fronthaul link is implemented by means of a ring-shaped optical fiber link, with the corresponding allocated PRB group AGg,nAssociation A togetherSSD and assignment ALLD provisioning and transport enabling RU to remote unitsjDynamic routing is provided, thus greatly reducing the forwarding load. In addition, due to the association ASSD and assignment ALLD data and PRB pair PPRBpTransmitted together (e.g., before) so that to/from multiple remote units RU are enabledjStatistical multiplexing of data (i.e., if the remote unit RUjWith less loadCapacity may be dynamically allocated to other remote units RU connected to the same fronthaul linkj) And to the received PRB pair PPRBpRemapping to RU at remote unitjSide reconstruction of correct time-frequency grid TFGnIs possible.
Thus, relative to where N isSTime-frequency grid TFGnThe present invention allows a known solution (and in particular the solution disclosed in WO 2010/075864) of column-by-column transmission in the frequency domain, even when empty (empty) or almost empty (i.e. when only control data has to be transmitted in case of low load periods), allowing a time-frequency grid TFGnTransmitting only the allocated PRB pair PPRBpThus enabling the forward payload to be transmitted to the user equipment UEiIs proportional to the payload of (a).
It is noted that the method proposed in the present invention does not compress the data to be transmitted over the fiber link FLiThe data transmitted, thus ensuring that the RU is at the remote unitjThe side is the same "quality of service" (QoS) as the one experienced at the side of the central unit CU.
In addition, by association ASSD and assignment ALLThe additional bits provided by the D data do not significantly affect the data throughput (and, however, it is largely compensated by the savings in transmission capacity). In practice, consider for example a remote unit RU that can be connected to a central unit CUjIs equal to 128 (i.e. the associated data is a 128-bit bitmap), the signalling burden will be equal to 128kbps (i.e. 128 bits per 1ms subframe), which is negligible. Similarly, considering for example a bitmap with allocation data of N bits (N being the number of allocated PRB pairs contained in a subframe), the corresponding signalling burden will be equal to N kbps (i.e. N bits per 1ms subframe), which is still negligible.
Naturally, to satisfy local and specific requirements, a person skilled in the art may apply to the solution described above many logical and/or physical modifications and alterations. More specifically, although the present invention has been described with a certain degree of particularity with reference to preferred embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as in other embodiments are possible. In particular, various embodiments of the invention may be practiced without even the specific details set forth in the preceding description to provide a more thorough understanding thereof; rather, well-known features may have been omitted or simplified in order not to obscure the description with unnecessary detail. Moreover, it is expressly intended that specific elements and/or method steps described in connection with any disclosed embodiment of the invention may be incorporated in any other embodiment as a matter of general design choice.
More specifically, the solution according to the embodiments of the invention is suitable to be implemented by equivalent methods (by using similar steps, removing some steps that are not essential, or adding further optional steps); further, the steps may be performed in a different order, simultaneously or in an interleaved manner (at least partially).
In addition, similar considerations apply if the mobile network has a different structure or comprises equivalent components, or it has other operating characteristics. In any case, any of its components may be divided into several elements, or two or more components may be combined into a single element; in addition, each component may be duplicated for supporting parallel execution of the corresponding operation. It should also be noted that any interaction between different components need not be continuous in general (unless otherwise indicated), and that it can be both direct and indirect through one or more intermediaries.
Furthermore, although reference has been made explicitly to mobile networks based on the LTE standard, it should be understood that applicant's intent is not to be limited to the implementation of any particular mobile network architecture or protocol. Considering, for example, the evolution of the LTE/LTE-a standard providing narrowband control data flows for the carrier currently in question, a complete "switch-off" of the allocated PRB pair is foreseen to be controlled. In this way, according to the exemplary protocol defined above, no fronthaul transmission capacity will be required for controlling the transmission of the allocated PRB pairs.
Furthermore, although fiber optic links have been specifically mentioned in this specification, this should not be construed restrictively. Indeed, the principles of the present invention may also be applied in scenarios where the fronthaul link is managed by means of a wireless link rather than a fiber optic link.
Finally, the method can also be easily applied to systems other than OFDMA-based systems. By way of example only, in the case of a system based on CDMA ("code division multiple access") technology, such as a 3GPP UMTS/HSDPA system, the principles of the invention described above may be applied with simple modifications. For example, in view of the teachings of the present invention, a skilled person may operate to perform spreading and scrambling operations in a remote unit, thereby enabling different user signals to be transmitted as separate signals in a fronthaul link. This will allow the transmission of only the signals of the users actually allocated for transmission, with the obvious advantage that the transmission rate on the fronthaul link will become proportional to the actual load on the radio interface. This, in turn, will allow statistical multiplexing/load balancing to be performed between remote units connected to the same fronthaul network.

Claims (14)

1. A method of arranging transmission of data between user equipment and at least one base station in a mobile communications network, the at least one base station comprising a central unit and a plurality of remote units associated with the central unit, the method comprising:
for each respective remote unit of the plurality of remote units, allocating one or more radio resources for data to/from the respective remote unit, wherein the data comprises information data and control data from a central unit to the respective remote unit or from the respective remote unit to a central unit,
for each respective remote unit, grouping the allocated one or more radio resources into an allocated set of radio resources, the allocated set of radio resources comprising at least one radio resource allocated for data to/from the respective remote unit,
including association data in the allocated set of radio resources for each respective remote unit, the association data indicating an association of the allocated at least one radio resource of the allocated set of radio resources with the respective remote unit,
including allocation data in the allocated set of radio resources for each respective remote unit, the allocation data indicating the allocated one or more radio resources that have been allocated at least for information data, an
For each respective remote unit, transmitting the allocated set of radio resources in the frequency domain between the central unit and the respective remote unit, wherein unallocated radio resources are not transmitted.
2. The method of claim 1, wherein transmitting the allocated set of radio resources in the frequency domain between a central unit and the respective remote unit comprises: for each allocated set of radio resources, only the allocated radio resources that have been allocated at least for information data among the allocated one or more radio resources of the allocated set of radio resources are transmitted.
3. A method according to claim 1 or 2, wherein the association data comprises a number of bits depending on the maximum number of remote units that can be associated with the central unit, each bit being associated with a respective remote unit and being set to a first logical value if the allocated radio resource or resources of the allocated set of radio resources under consideration are associated with that remote unit and to a second logical value otherwise.
4. A method according to claim 3, wherein the allocation data comprises a number of bits depending on the maximum number of radio resources available for allocation, each bit being associated with a respective radio resource and being set to a first logical value if at least the respective radio resource has been allocated for the information data and to a second logical value otherwise.
5. The method of claim 4, wherein allocating data further comprises at least one further bit associated with each radio resource, the at least one further bit providing an indication of a modulation scheme used to modulate data on the allocated one or more radio resources.
6. The method of claim 1, wherein transmitting the allocated set of radio resources in the frequency domain between a central unit and the respective remote unit for each respective remote unit comprises transmitting each set of radio resources in turn.
7. The method of claim 1, wherein transmitting the allocated set of radio resources in the frequency domain between a central unit and the respective remote unit comprises transmitting association data and allocation data for each set of radio resources before the allocated one or more radio resources for that set of radio resources.
8. The method of claim 1, wherein the data is orthogonal frequency division multiplexing data.
9. The method of claim 1, wherein the grouping, the including association data, and the including allocation data are performed on a central unit side when a set of radio resources is transmitted from a central unit to the respective remote unit, and on at least one remote unit side when a set of radio resources is transmitted from the respective remote unit to a central unit.
10. A system for exchanging data with user equipment in a mobile communications network, the system comprising a central unit adapted to be associated with a plurality of remote units, the central unit being configured to:
for each respective remote unit of the plurality of remote units, allocating one or more radio resources for data destined for the respective remote unit, wherein the data comprises information data and control data from a central unit to the respective remote unit,
for each respective remote unit, grouping the allocated one or more radio resources into an allocated set of radio resources, the allocated set of radio resources comprising at least one radio resource allocated for data destined for the respective remote unit,
including association data in the allocated set of radio resources for each respective remote unit, the association data indicating an association of the allocated at least one radio resource of the allocated set of radio resources with the respective remote unit,
including allocation data in the allocated set of radio resources for each respective remote unit, the allocation data indicating the allocated one or more radio resources that have been allocated at least for information data, an
For each respective remote unit, transmitting the allocated set of radio resources in the frequency domain between the central unit and the at least one remote unit, wherein unallocated radio resources are not transmitted.
11. The system of claim 10, further comprising one or more of the plurality of remote units.
12. The system of claim 11, wherein the one or more remote units are connected to the central unit by a fiber optic link.
13. The system of claim 11, wherein the one or more remote units are connected to the central unit by a wireless communication link.
14. A non-transitory computer-readable medium comprising software code portions stored thereon, which when executed by at least one computer, cause the at least one computer to perform the method of any one of claims 1-9.
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